We have focused our attention on the cyanobacterial responses to metals such as zinc and copper as well as cellular responses to the oxyanions of arsenic (arsenate and arsenite). Metallothioneins are sulfur rich proteins expressed by eukaryotic cells in response to metal challenges. These proteins sequester, thus detoxify the metal ions. The only bacterial metallothionein reported is that from Synechococcus sp PCC7942. We developed PCR primers base on this gene sequence and have found that these genes (smtA/smtB) are present in filamentous cyanobacterial strains isolated from metal contaminated soils. These cyanobacterial strains have also been shown to possess a number of plasmids where metal resistance deteminants are often encoded. It has been shown that arsenate is taken up by E coli and Staphylococcus sp cells via phosphate translocators of the bacterial cytoplasmic membrane. Toxic effects of this ion may include perturbation of normal phosphate metabolism in reactions such as nucleic acid polymerization and the ATP utilizing reactions of the cell. These bacteria reduce arsenate intracellularly to less toxic arsenite and actively pump arsenite out of cells via an ATP dependent arsenite pump. We propose that the high affinity phosphate translocator does not distinguish phosphate from arsenate as clearly as the constituitive phosphate translocator.